1. Field of the Invention
The field of the present invention is camera dollies.
2. Background
Camera dollies are used in the television and motion picture industries to support and maneuver a camera. Typically, the camera dolly is on wheels and has an arm to raise and lower the camera. The camera dolly is generally moved by dolly operators or xe2x80x9cgripsxe2x80x9d, to properly position the camera to follow the film or video sequence.
The camera dolly must support and maneuver the camera with a minimum of vibration or shock to avoid degrading the filmed image quality. Consequently, camera dollies must be designed, manufactured, and maintained with precision. When used on a relatively smooth surface, such as studio floors, the camera dolly is generally supplied with pneumatic tires, or smooth precision tires of various materials, so that the camera may be smoothly supported and moved, even over minor cracks or bumps in the floor surface.
When the supporting ground surface is bumpy and irregular (e.g., when the dolly is used outdoors on sand, irregular ground, a poor quality paved surface, etc.,) track is assembled on the ground to provide a smooth rolling surface for the dolly. However, for use on track, many dollies require that the pneumatic ground wheels be replaced with stiffer track wheels. Other camera dollies require the installation of track wheel attachments, which are provided as accessories to the dolly. While these techniques have met with varying degrees of success, they have certain disadvantages. For example, it may be time consuming and labor intensive to install track wheels. During production of a motion picture or television program, even a delay of five minutes (e.g., to install track wheels) can be very costly, as all the actors, camera operators, lighting, sound and special effects professionals, the director, and the various crew members must wait until the camera dolly is set up for the track filming sequence. Accordingly, it is advantageous to have equipment which can be quickly set up for the desired film or video sequence. In addition, track wheels or track wheel attachments must often be shipped and stored separately from the camera dolly since they are not permanently attached to the dolly. This requirement further complicates the logistics of television and film production.
Where a camera dolly is moved over curved track, the lateral spacing between the left and right wheels (or sets of wheels) must be allowed to change slightly, to accommodate the wheel position geometry on curved track. In addition, the wheel (or wheel sets) on the inside of the curve must be turned or angled more sharply than the outside wheels. These requirements must be accommodated for good dolly performance, and they complicate dolly design considerations.
U.S. Pat. No. 5,609,108, incorporated herein by reference, discloses one type of system that may be used to make using camera dollies with track more convenient. In this design, a camera dolly includes a kingpin pivotably supported on a chassis. A kingpin tube extends laterally from the kingpin and an axle is supported within the kingpin tube by two axle pins, thus allowing the axle to pivot slightly on the axle pins. A wheel bearing supporting a track wheel is mounted on the axle. A knob is threaded into the end of the axle such that the knob, when in a first position limits the lateral movement of the track wheel and the pivoting of the axle. In the second position, the track wheel may shift laterally and the axle may pivot, thus permitting the track wheels to be used on curved track without binding. However, under certain circumstances, this design may be too bulky to meet the needs of the dolly operator and film crew, especially because the knob protrudes out beyond the overall envelope in volume of the dolly. Threading the knob in and out can also be time consuming.
Accordingly, there is a need for an improved track wheel system for camera dollies.
The present invention is directed to an improved track wheel system for a camera dolly. In a first aspect, a kingpin is pivotably attached to the dolly chassis. An axle is attached to the kingpin. A wheel is supported on the axle. A spacer is placed on the axle between the end of the axle and the wheel. A stop, preferably a quick release clip, is attached to the end of the axle. In using a quick release clip, the spacer may be removed quickly and easily. After removing the spacer, the quick release clip is replaced. Without the spacer, the track wheel is free to shift laterally on the axle.
By providing a track wheel system with track wheels that can shift laterally on the axle, the system allows the camera dolly to roll on curved track without binding. The dolly may also be conveniently used on ground as the installation of the spacer prevents the track wheel from shifting. Thus, the track wheel system for the camera dolly disclosed herein does not require the wheels to be changed when being used on ground or track. The spacer can be quickly removed or replaced, minimizing the time required to convert the dolly for use on track. Only two wheel spacers, preferably on the same side of the dolly, need be removed. This saves time and works well to stabilize the dolly.